Electrophoretic display devices that take advantage of the electrophoretic phenomenon are known as non-emissive display devices. The electrophoretic phenomenon refers to the phenomenon in which when an electric field is applied to a suspension composed of a liquid phase dispersion medium with fine particles dispersed therein, the particles, which are naturally charged through dispersion (electrophoretic particles), migrate due to a Coulomb force.
In a basic structure of the electrophoretic display device, one electrode and another electrode are facing each other with a predetermined spacing, and the above-described suspension (electrophoretic suspension) is enclosed therebetween.
Furthermore, at least one electrode is transparent, and this transparent electrode side serves as an observation surface. When a potential difference is applied between these two electrodes, electrophoretic particles are attracted to either of the electrodes, depending on the direction of the electric field.
Consequently, in this structure, when the dispersion medium is dyed with a dye and the electrophoretic particles are composed of pigment particles, either the color of the electrophoretic particles or the color of the dye can be observed, depending on the direction of the electric field through the transparent observation surface. Therefore, an image can be displayed by forming the electrode with a pattern in accordance with each pixel, and controlling a voltage applied to each pixel electrode.
Such an electrophoretic display device is noted as an electro-optical apparatus suitable for a new display because of the advantages of a simple configuration, a wide viewing angle range, a low power consumption, a display image holding performance (hereafter referred to as “memorization property”), and the like.
A microcapsule type electrophoretic display device is an example of an electrophoretic display device (for example, refer to the following Patent literature 1). In this device, a plurality of microcapsules containing an electrophoretic suspension are disposed between a pair of electrodes. In this device, a capsule film of each microcapsule is composed of, for example, a mixture of gelatin and gum Arabic. This microcapsule is fixed between the electrodes with a binder made of a silicone resin, an acrylic resin, an urethane resin or the like. See, for example, Japanese Unexamined Patent Application Publication No. 1-86116.
However, conventional electrophoretic display devices are susceptible to improvement in the compatibility between the memorization property and the erasability. That is, when the application of a voltage is stopped after an image is displayed by application of the voltage, the displayed image disappears in a short time. On the other hand, when the memorization property is improved, erasure is not easily performed due to phenomena such as image persistence, and rewrite of the display becomes difficult.